llvm dev - Jul 2017 - Conditional Register Assignment based on the no of loop iterations

hello,

i have a situation where i have to assign the registers to instructions
based on the loop iterations.

for eg..
the registers are:
R_0_V_0, R_0_V_1, R_0_V_2, R_0_V_3,
R_1_V_0, R_1_V_1, R_1_V_2, R_1_V_3,
R_2_V_0, R_2_V_1, R_2_V_2, R_2_V_3.
These registers defined in object Reg_A

These are total 12 registers. will use them contiguously, here i  define it
in above mentioned order i.e changing V first then R.


for eg;
if no of iterations>=4.
1st load will take place in R_0_V_0
2nd load will take place in R_0_V_1
3rd load will take place in R_0_V_2
4th load will take place in R_0_V_3
I am getting this required behavior for iterations>=4. I want this to
happen only if there are 4 or above iterations in loop.


But if my iterations are less than 4 like 3
again it will do the same thing;
1st load will take place in R_0_V_0
2nd load will take place in R_0_V_1
3rd load will take place in R_0_V_2

Here i dont want the above to happen rather it should increment R instead
of V in this case.
It should do something as follows:
1st load to take place in R_0_V_0
2nd load to take place in R_1_V_0
3rd load to take place in R_2_V_0

Now, how to achieve this?

Can i mention some condition in instructioninfo.td file?
and in registerinfo.td file instead of 1 object Reg_A, there will be 2
objects Reg_A and Reg_B
where Reg_B defines same registers but in different order.

Reg_B;

R_0_V_0, R_1_V_0, R_2_V_0,  //here R changes
R_0_V_1, R_1_V_1, R_2_V_1,
R_0_V_2, R_1_V_2, R_2_V_2,
R_0_V_3, R_1_V_3, R_2_V_3.

So that in instructioninfo.td file it will be something like;

if (no of iterations>=4)

load ................$Reg_A      ; here all register operands will come
from Reg_A instance.

if (no of iterations<4)

load ................$Reg_B      ; here all register operands will come
from Reg_B instance.


Is the above approach possible??? if yes then how can we acquire the no of
iterations in instructioninfo.td file??

or can you suggest some better way?

Looking forward to response

Thank You.
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or should i write a condition in registerinfo.td; to define the registers
in object Reg_A in specific order according to loop iterations.

On Mon, Jul 10, 2017 at 9:17 AM, hameeza ahmed <hahmed2305 at gmail.com>
wrote:
> hello,
>
> i have a situation where i have to assign the registers to instructions
> based on the loop iterations.
>
> for eg..
> the registers are:
> R_0_V_0, R_0_V_1, R_0_V_2, R_0_V_3,
> R_1_V_0, R_1_V_1, R_1_V_2, R_1_V_3,
> R_2_V_0, R_2_V_1, R_2_V_2, R_2_V_3.
> These registers defined in object Reg_A
>
> These are total 12 registers. will use them contiguously, here i  define
> it in above mentioned order i.e changing V first then R.
>
>
> for eg;
> if no of iterations>=4.
> 1st load will take place in R_0_V_0
> 2nd load will take place in R_0_V_1
> 3rd load will take place in R_0_V_2
> 4th load will take place in R_0_V_3
> I am getting this required behavior for iterations>=4. I want this to
> happen only if there are 4 or above iterations in loop.
>
>
> But if my iterations are less than 4 like 3
> again it will do the same thing;
> 1st load will take place in R_0_V_0
> 2nd load will take place in R_0_V_1
> 3rd load will take place in R_0_V_2
>
> Here i dont want the above to happen rather it should increment R instead
> of V in this case.
> It should do something as follows:
> 1st load to take place in R_0_V_0
> 2nd load to take place in R_1_V_0
> 3rd load to take place in R_2_V_0
>
> Now, how to achieve this?
>
> Can i mention some condition in instructioninfo.td file?
> and in registerinfo.td file instead of 1 object Reg_A, there will be 2
> objects Reg_A and Reg_B
> where Reg_B defines same registers but in different order.
>
> Reg_B;
>
> R_0_V_0, R_1_V_0, R_2_V_0,  //here R changes
> R_0_V_1, R_1_V_1, R_2_V_1,
> R_0_V_2, R_1_V_2, R_2_V_2,
> R_0_V_3, R_1_V_3, R_2_V_3.
>
> So that in instructioninfo.td file it will be something like;
>
> if (no of iterations>=4)
>
> load ................$Reg_A      ; here all register operands will come
> from Reg_A instance.
>
> if (no of iterations<4)
>
> load ................$Reg_B      ; here all register operands will come
> from Reg_B instance.
>
>
> Is the above approach possible??? if yes then how can we acquire the no of
> iterations in instructioninfo.td file??
>
> or can you suggest some better way?
>
> Looking forward to response
>
> Thank You.
>
>
>
>
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Here basically my problem is vector width since i have used v64i32 in my
backend. now if vector width=64. i want the Reg_B class registers to be
assigned and if vector width=2048 i want Reg_A registers to be assigned to
instruction.

Should i incorporate the solution in lowering stage? some thing like;

addRegisterClass(MVT::v2048i32, &X86::Reg_B);

              setOperationAction(ISD::MNLOAD,               MVT::v2048i32,
custom);

then in function LowerOperation(SDValue Op, SelectionDAG &DAG)

i should do,

  case ISD::MNLOAD:               return LOAD2048(Op, Subtarget, DAG);

then i will implement
static SDValue LOAD2048(SDValue Op, const X86Subtarget &Subtarget,
                          SelectionDAG &DAG)
{

//dont know the details of this part
but here i plan to encode 2048 elements again in 32 v64i32 but with
different instruction name like previously it was
load<LD256; i intend to make it load<LD256_N

so that in instructioninfo.td while pattern matching both LD256 and LD256_N
are treated separately. 1 will use Reg_B registers and other will use Reg_A
respectively.


Is it fine???
Please guide me...
I need serious help, please.....

Thank You



On Mon, Jul 10, 2017 at 9:29 AM, hameeza ahmed <hahmed2305 at gmail.com>
wrote:
> or should i write a condition in registerinfo.td; to define the registers
> in object Reg_A in specific order according to loop iterations.
>
> On Mon, Jul 10, 2017 at 9:17 AM, hameeza ahmed <hahmed2305 at
gmail.com>
> wrote:
>
>> hello,
>>
>> i have a situation where i have to assign the registers to instructions
>> based on the loop iterations.
>>
>> for eg..
>> the registers are:
>> R_0_V_0, R_0_V_1, R_0_V_2, R_0_V_3,
>> R_1_V_0, R_1_V_1, R_1_V_2, R_1_V_3,
>> R_2_V_0, R_2_V_1, R_2_V_2, R_2_V_3.
>> These registers defined in object Reg_A
>>
>> These are total 12 registers. will use them contiguously, here i 
define
>> it in above mentioned order i.e changing V first then R.
>>
>>
>> for eg;
>> if no of iterations>=4.
>> 1st load will take place in R_0_V_0
>> 2nd load will take place in R_0_V_1
>> 3rd load will take place in R_0_V_2
>> 4th load will take place in R_0_V_3
>> I am getting this required behavior for iterations>=4. I want this
to
>> happen only if there are 4 or above iterations in loop.
>>
>>
>> But if my iterations are less than 4 like 3
>> again it will do the same thing;
>> 1st load will take place in R_0_V_0
>> 2nd load will take place in R_0_V_1
>> 3rd load will take place in R_0_V_2
>>
>> Here i dont want the above to happen rather it should increment R
instead
>> of V in this case.
>> It should do something as follows:
>> 1st load to take place in R_0_V_0
>> 2nd load to take place in R_1_V_0
>> 3rd load to take place in R_2_V_0
>>
>> Now, how to achieve this?
>>
>> Can i mention some condition in instructioninfo.td file?
>> and in registerinfo.td file instead of 1 object Reg_A, there will be 2
>> objects Reg_A and Reg_B
>> where Reg_B defines same registers but in different order.
>>
>> Reg_B;
>>
>> R_0_V_0, R_1_V_0, R_2_V_0,  //here R changes
>> R_0_V_1, R_1_V_1, R_2_V_1,
>> R_0_V_2, R_1_V_2, R_2_V_2,
>> R_0_V_3, R_1_V_3, R_2_V_3.
>>
>> So that in instructioninfo.td file it will be something like;
>>
>> if (no of iterations>=4)
>>
>> load ................$Reg_A      ; here all register operands will come
>> from Reg_A instance.
>>
>> if (no of iterations<4)
>>
>> load ................$Reg_B      ; here all register operands will come
>> from Reg_B instance.
>>
>>
>> Is the above approach possible??? if yes then how can we acquire the no
>> of iterations in instructioninfo.td file??
>>
>> or can you suggest some better way?
>>
>> Looking forward to response
>>
>> Thank You.
>>
>>
>>
>>
>
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